JPH0546892B2 - - Google Patents

Description

Claim 1: An apparatus 10 for controllably testing the brakes of a wheeled vehicle in response to receiving a brake test command signal, the vehicle comprising: a power source 46; a transformer having a traction motor 52 controllably connected thereto, a vehicle brake 12 associated with at least one vehicle wheel, and for generating a wheel rotation signal in response to rotation of the at least one vehicle wheel; a regulator means 40; an actuator means 18 for controllably engaging and disengaging said vehicle brake 12 in response to respective receipt of brake engagement and disengagement control signals; and said brake test. generating said brake engagement control signal in response to and receiving a command signal, and transmitting said brake engagement control signal to said actuator means 18 to engage said vehicle brake 12;
A predetermined amount of power is supplied to the power source 46 for a predetermined period of time.
to the traction motor 52 to receive the vehicle rotation signal from the transducer means 40 to measure the angle of rotation of the vehicle wheel during a predetermined portion of the predetermined period; and processor means 54 for generating a brake condition signal in response to the measured rotation angle.

2. The apparatus of claim 1, wherein the power delivered from the power source 46 to the traction motor 52 is controllably adjusted to produce a predetermined amount of traction motor torque.

3. Processor means 54 generates a first vehicle brake status signal in response to an angle of rotation of a vehicle wheel during a predetermined portion of a predetermined period of time being less than a predetermined amount; Apparatus 10 according to claim 1, wherein the second vehicle brake condition signal is generated in response to the rotation angle of the wheel being not less than the predetermined amount.

4. The transducer means 40 includes a resolver for a rotary resolver 42 and a digital converter 44 associated with one of the vehicles and adapted to generate a digital signal responsive to the angle of rotation of said wheel. Apparatus 10 according to item 1.

5. The vehicle receives a remotely generated brake test command signal, responsively transmits said brake test command signal to processor means 54, receives a brake condition signal from said processor means 54, and responsively receives said brake test command signal from said processor means 54; Apparatus 10 according to claim 1, further comprising electromagnetic signal transmitting and receiving means 58, 60 for transmitting said brake condition signal as an electromagnetic signal.

6. In a method for controllably testing the brakes of a wheeled vehicle, the vehicle is equipped with a power source 46.
a main motor 52 connected to the power source 46 and at least one vehicle wheel; a vehicle brake 12 associated with the at least one vehicle wheel; and a wheel rotation angle transducer 40 connected to the at least one vehicle wheel. a step of engaging the vehicle brake 12; a step of supplying a predetermined amount of regulated electric power from the power source 46 to the main motor 52 to generate a predetermined amount of motor torque; receiving and storing a first wheel rotation angle signal from the wheel rotation transducer 40 at one predetermined time; and receiving and storing a first wheel rotation angle signal from the wheel rotation transducer 40 at a second predetermined time after the first predetermined time. receiving and storing a second wheel rotation angle signal; calculating an angle through which the vehicle wheel rotates during an interval between receiving the first and second wheel rotation signals; generating a first brake condition signal in response to the angle of rotation being less than the predetermined amount; and generating a second brake condition signal in response to the angle of rotation being not less than the predetermined amount. Test method.

TECHNICAL FIELD This invention relates generally to apparatus and methods for testing vehicle brakes, and more particularly to controllably testing the brakes of a motorized vehicle and generating a brake status signal in response to the status of the brakes. The present invention relates to an apparatus and method for generating.

BACKGROUND OF THE INVENTION Virtually all motor vehicles in use today have some type of accessory braking system, typically of the disc or drum type associated with one or more wheels of the vehicle. consisting of either mechanical brakes. The brake is mechanically, hydraulically, or electrically actuated, and generally is something placed in contact with a rotating member of the vehicle to create sufficient friction to stop the vehicle. It has different types of friction materials. The brake system is subjected to various conditions that may result in less braking than desired. For example, the friction material may wear to the point that it no longer provides sufficient friction to stop the vehicle within the recommended distance, or significant delays may occur due to electrical or hydraulic failures.

In a driver-controlled vehicle, such as a typical industrial lift truck, deterioration of the control system is quickly detected by the driver and appropriate maintenance actions are taken. However, today's manufacturing operations require the deployment of unmanned vehicles for specific applications. For example, in the field of materials handling, unmanned vehicles can be advantageously used to move materials from one point throughout an industrial facility. Such unmanned vehicles are typically controlled by one or more on-board computer systems, which are often in communication with a stationary master computer system. The master computer and the on-board computer communicate with each other via some type of link, such as a wireless transceiver.

In the case of such unmanned vehicles, it is particularly important to keep the attached braking devices in good working condition. However, it is difficult to objectively measure the vehicle braking condition at a particular time without driver intervention. Therefore, in order to realize the potential of unmanned vehicles, it is necessary to develop tests for vehicle braking that can be performed automatically at frequent intervals by the vehicle computer system.

The present invention seeks to overcome one or more problems as set forth above.

DISCLOSURE OF THE INVENTION In one aspect of the invention, an apparatus for controllably testing the brakes of a wheeled vehicle is provided. The vehicle has a power source, a traction motor controllably connected to the power source and to at least one vehicle wheel, and a vehicle brake associated with the at least one vehicle wheel. Transducer means is provided for generating a wheel rotation signal in response to rotation of at least one vehicle wheel, and in response to receiving each of a brake engagement control signal and a brake disengagement control signal. Actuator means are provided for controllably engaging and disengaging the vehicle brake.
receiving a brake test command signal, responsively generating a brake engagement control signal and a brake disengagement control signal, and transmitting a brake engagement signal to said actuator means for engaging said vehicle brake. Processor means are provided. The processor means supplies a predetermined amount of power from the power supply to the traction motor over a predetermined period of time. The processor means receives the wheel rotation signal generated by the transducer means and measures the angle of rotation of the vehicle wheel during a predetermined portion of the predetermined period of time. Finally, the processor means generates a brake status signal in response to the measured vehicle wheel rotation angle.

In a second aspect of the invention, a method is provided for controllably testing the brakes of a wheeled vehicle. The vehicle includes a power source, a traction motor controllably connected to the power source and to at least one vehicle wheel, a vehicle brake associated with the at least one vehicle wheel, and a vehicle brake connected to the at least one vehicle wheel. It has a wheel rotation transducer. The method includes engaging the vehicle brakes and supplying a regulated amount of power from the power source to the traction motor to generate a predetermined amount of motor torque. First and second wheel rotation signals from the wheel rotation transducer are received and stored at first and second predetermined times. The stored first and second wheel rotation signals are then used to calculate the angle through which the vehicle wheel rotates during the interval between reception of the first and second wheel rotation signals. Finally, a first brake condition signal is generated in response to said angle of rotation being less than a predetermined amount, and said angle of rotation being equal to or greater than said predetermined amount; A second brake status signal is generated in response to being not less than .

The present invention provides an objective brake test that can be performed automatically by an on-board vehicle computer system. This test procedure can be performed at predetermined intervals, for example, prior to vehicle movement following a cold start, or it can be performed in response to commands from a master computer system or manual test inputs. .

[Brief explanation of the drawing]

For a better understanding of the invention, reference is made to the accompanying drawings.

In the drawings, FIG. 1 is a schematic diagram of one embodiment of the present invention, and FIGS. 2 to 5 are flowcharts of software used in one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an apparatus embodying some of the principles of the invention is indicated at 10. The following detailed description is of a preferred embodiment of apparatus 10. However, the apparatus 10 may take many other forms, as will be apparent to those skilled in the art, without departing from the scope of the appended claims.

FIG. 1 is a schematic diagram of one embodiment of the invention, including the necessary components of a typical vehicle. Vehicle brake 12 includes a brake drum 14, brake pads 16, and actuator means 18. Actuator means 18 includes, for example, a bell crank 20 pivotally mounted between brake shoe or pad 16 and a stationary portion 22 of the vehicle. The bellcrank 20 is biased by a spring 24 to keep the brake shoe 16 in constant engagement with the brake drum 14. A solenoid 26 is connected to a piston of a hydraulic cylinder 28. Solenoid 26 controllably engages and disengages vehicle brake 12 in response to the state of solenoid 26 and the position of the piston of hydraulic cylinder 28 .

Movement of the hydraulic cylinder piston is responsive to the flow of hydraulic fluid through the hydraulic pump 30 through the directional shuttle valve 32. The direction of flow of the hydraulic fluid is controlled by electrically biasing shuttle valve 32 in one direction or the other in response to conduction of one or the other of a pair of transistors 34, 36. Ru. Activation of solenoid 26 is controlled by the state of another transistor 38.

The device 10 also includes transducer means 40 for generating a vehicle rotation signal in response to rotation of at least one of the vehicle wheels. The transducer means 40 comprises, for example, a resolver 42 connected to one of the vehicle wheels and a resolver 44 to a digital converter connected to said resolver.

The vehicle also has a power source 46, such as a battery 48. A power drive switch 50, such as a plurality of power transistors, is connected in series between battery 48 and traction motor 52. Main electric motor 52 is associated with one or more drive wheels of the vehicle.

Processor means 54 is, for example, a microprocessor 56 of the type commonly commercially available today. Microprocessor 56 may be dedicated to device 10 or may be part of the overall vehicle control computer system. Processor means 54 has a plurality of input and output ports connected to various peripheral devices. For example, input port PI-1 is connected to resolver 44 for a digital converter. The first output port PO-1 is connected to a solenoid drive transistor 38. Similarly, the output port
PO-2 and PO-3 are connected to shuttle valve drive transistors 36 and 34, respectively. Fourth
The output port PO-4 is connected to the drive motor power switch 50.

Finally, in one embodiment of the invention, processor means 54 includes a suitable communications interface 58.
It has an input/output port PIO-1 connected to the vehicle transceiver 60 via. Vehicle transceiver 6
0 is, for example, a customary radio frequency transmitter and receiver. A corresponding remote computer transceiver 62 to facilitate communication between processor means 54 and a remote master computer system.
may be provided.

Industrial Applicability FIGS. 2-5 are flowcharts of software intended for use with the embodiment of the invention shown in FIG. The software described above is particularly intended for use with processor means 54. The operation of apparatus 10 will be described in detail for use on a vehicle, such as an unmanned industrial vehicle. In the following discussion of the software program of FIGS. 2-5, it will be helpful to refer to the associated hardware components shown in FIG.

The software program shown in FIGS. 2-5 enables processor means 54 to perform at least the following functions. Processor means 54 generates brake engagement control signals and brake disengagement control signals and sends brake engagement control signals to actuator means 18, thus engaging vehicle brakes 12. Processor means 54 is then regulated to controllably supply a predetermined amount of power from power supply 46 to traction motor 52, thus producing a predetermined amount of motor torque at the vehicle wheels. After a first predetermined period of time has elapsed following application of power from power source 46, a first wheel rotation angle signal is received from transducer means 40, and the received wheel rotation angle signal is transmitted to a predetermined computer. stored in a register. After a second predetermined period of time has elapsed, a second wheel rotation angle signal is received from the transducer means 40 and likewise stored in a predetermined computer register.

Processor means 54 uses the stored first and second wheel rotation angle signals to
calculate the rotation angle through which the vehicle wheels rotate during the interval between reception of the wheel rotation signals. Processor means 54 then generates a first brake status signal in response to said calculated angle of rotation being less than a predetermined amount, e.g. 10 degrees; A second brake condition signal is generated in response to being equal to or greater than the second brake condition signal.

One particular implementation of the software program is block 10 in FIG.
Starts with 0. Block 100 is the starting point for the software routine that performs the autobrake test. In the preferred embodiment of the invention, the software routine beginning at block 100 includes:
In response to receiving a brake test command signal remotely generated by the master command computer system, transmitted from remote computer transceiver 62 to vehicle transceiver 60, and transmitted via communication interface 58 to port PIO-1, the processor It is initiated by means 54.

At block 102, a logic ``0'' is output by processor means 54 at port PO-1. This signal turns off transistor 38 and deenergizes solenoid 26. In response, the plunger of solenoid 26 is retracted from bellcrank 20 by a conventional internal solenoid spring, causing brake shoe 16 to engage brake drum 14.

The work within processor means 54 generally occurs with specific memory registers designated by alphanumeric symbols in the following description. At block 104, the literal number or count "256" is entered into register "B". Block 105 simply
It is the entry point into the flow of this computer program and will be referenced later in the program.

At block 106, a logic ``1'' indicates that the port
Sent to PO-4. This turns on the drive motor switch means 50 and begins the process of supplying power from the power source 46 to the traction motor 52. Next, register "A" is loaded with a predetermined pulse "on" count at block 108;
It is then decremented by one in block 110. Register "A" is then examined at block 112 to determine whether it has counted down to the number "0" and a loop is entered until such time as register "A" equals "0". At block 112 register "A"
When it is found that becomes equal to '0',
In block 114, logic ``0'' indicates port PO.
-4. This is a motor or main electric motor 52
and register "B" is decremented by one at block 116.

At block 118, register "B" is checked to determine if it is equal to the number "128". If so, the value provided by the resolver to digital converter 44 at port PI-1 is read into register "C" at block 120. Register "B" is then checked at block 122 to see if it is equal to the number "0". If register "B" is not equal to "128" at block 118, control passes immediately to test block 122. If register "B" is not equal to "0" at block 122, register "F" is loaded with a pulse "off" count at block 124. Register "F" is then decremented by one at block 126 and tested at block 128 to see if it has become equal to "0." If this is not the case, register "F" continues to be decremented at block 126 until such time as the register equals "0".
Control then returns to the entry point shown as block 105. If register "B" is equal to "0" in block 122, then
Control passes to block 130 where the value from the resolve to digital converter 44 is again read at port PI-1 and stored in register "D".

Wheel rotation is then clocked at 132 using the values already stored in registers "C" and "D".
Calculated in . In block 134,
Register "E" is loaded with the "brake check" status code and program control passes to block 136. If the wheel rotation calculated at block 132 is found to be less than the predetermined number of degrees at block 136, register "E" is reloaded at block 128 with a "brake OK" status code. If the calculated wheel rotation is equal to or greater than the predetermined amount, control passes directly from block 136 to block 140. In either case, the status code stored in register "E" is output as a signal at block 140. In the embodiment shown in FIG. 1, the brake status signal is sent to port PI-1 and then to communications interface 58. An electromagnetic representation of this status signal is then transmitted by vehicle transceiver 60 and received by master remote computer transceiver 62. In this way, the master remote computer transceiver is provided with status information regarding the condition of the vehicle brakes. Such information is useful, for example, in avoiding situations caused by worn brakes and in considering vehicle maintenance needs.

The brake condition signal described above may also be used in many other ways. For example, the condition signal may trigger various warning devices attached to the vehicle, such as flashing lights or audible signals, or cause further alarms on the vehicle until some prescribed action is taken. used to disable the operation of

In any event, once the brake test is complete, a logic ``1'' signal is output at block 142 to port PO--.
Sent to 2. In response, transistor 3
6 is energized and the shuttle valve 32 is moved to supply hydraulic fluid from the pump 30 to the hydraulic cylinder 28. This causes the piston of the cylinder 28 to retract, moving the solenoid 26 and causing the bell crank 2 to move.
Remove from engagement with 0. A delay in block 145 allows time for the piston to fully retract. Then, the logical value “1” is set to block 1.
44 to port PO-1 to re-extend the solenoid plunger. Block 1
At block 146, a logical ``0'' is sent to port PO-2 and a logical ``1'' is sent to port PO-3 at block 148. In response, transistor 36 is turned off and transistor 34
is turned on, again activating shuttle valve 32 and reversing the flow of hydraulic fluid from pump 30 to hydraulic cylinder 38. In response, solenoid 26 is moved relative to bellcrank 20 to extend spring 24 and remove brake shoe 16 from contact with brake drum 14 . The delay in block 149 allows time for complete release of the brake. Finally, block 150
, a logic "0" is sent to port PO-3,
The shuttle valve 32 is placed in a central or neutral position and the vehicle brake 12 is held in the disengaged position. The main vehicle control software program is then re-entered at block 152.

As those skilled in the art will appreciate, it is not essential for a given device to perform all of the steps shown in the flowcharts of FIGS. 2-5. Nor is it necessary to use a programmed microprocessor to perform the steps of FIGS. 2-5. However, suitable microprocessors are widely available on the market, understanding of programming techniques for microprocessors is widespread, the cost of microprocessor circuits in use has decreased in recent years, and programmable devices have become more widely available. Because of the flexibility afforded by its use, such an implementation is considered the best mode for carrying out the invention. Also, various other members in the embodiment shown in FIG. 1 may be replaced with functionally equivalent members. For example, vehicle brake 12 and actuator means 18 can be replaced by suitable electric braking equipment. Thus, at the expense of higher cost, the device is simplified by eliminating the hydraulic components and mechanical bellcrank 20 and associated equipment. Similarly, the resolvers for resolver 42 and digital converter 44 may be replaced with other suitable wheel transducers. Such modifications and substitutions may be made without departing from the scope of the appended claims.

Other aspects, objects, advantages, and uses of the invention will be apparent from a study of the drawings, disclosure, and appended claims.